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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="elem"> </div>
    <script>
        const elem = document.getElementById('elem');
        // elem.append(document.createTextNode('<b>hello</b>'));

        // elem.textContent = '<b>hello</b>'
        elem.innerHTML = '<b>hello</b>'
    </script>
</body>

</html>